STS-91 Day 2 Highlights

Discovery's crew has begun its first full day in orbit, a day
devoted to preparations for Thursday's final docking between a
U.S. Space Shuttle and the Russian Mir space station.

The crew was awakened this morning to "Shake, Rattle and Roll,"
performed by Huey Lewis and the News, in honor of Tuesday's flawless
liftoff. At the day's start, the crew -- Commander Charlie Precourt,
Pilot Dom Gorie and Mission Specialists Franklin Chang-Diaz, Wendy
Lawrence, Janet Kavandi and Valery Ryumin -- were about 2,600 miles
behind Mir, closing the distance between the two spacecraft by about
260 miles with each hour and a half-long orbit of Earth.

Later today, Precourt and Gorie will conduct additional planned
engine firings to refine Discovery's approach, and the crew will
install a centerline camera in Discovery's docking system to provide
Precourt with views of Mir docking targets during the rendezvous. The
crew will then conduct a check of all the equipment they will use
during tomorrow's activities. Discovery is planned to dock with Mir
at 11:58 a.m. CDT on Thursday.

Flight controllers noted a problem yesterday with transmissions from
Discovery's KU-band communications system, a system that uses a
dish-shaped antenna aboard the Shuttle to provide high-rate
communications, including television, to the ground. Although flight
controllers are continuing to troubleshoot the problem, at present the
system is unable to send television from the Shuttle or data from the
cargo bay experiments to the ground. Other operational modes of the
KU-band system are working properly. The system is able to receive
uplink transmissions from the ground and to operate as a rendezvous
radar system. Flight controllers believe a circuit, required to turn
the communications downlink system on, may not be working properly.

Late Tuesday, the crew powered up the Alpha Magnetic Spectrometer,
an astronomy instrument in Discovery's cargo bay that is planned to
look for "dark matter" that is theorized to comprise much of the
matter in the universe. The communications problem will not affect
the instrument's investigations since the data it gathers can be
recorded onboard the Shuttle for study after a return to Earth.

Flight controllers also are monitoring a water leak in a check valve
associated with one of Discovery's three fuel cells. The fuel cells
combine hydrogen and oxygen to generate electricity for the Shuttle,
and, as a byproduct, create water. The water produced by the fuel
cell's operation is normally routed to storage tanks, but the valve
problem is allowing some water to leak overboard. The valve problem
was known to controllers prior to Discovery's launch and is not a
problem for Thursday's docking with Mir. Discovery is in a 207 by 200
mile orbit.

Discovery'sastronauts spent much of today preparing for Thursday's
docking with the Mir space station and their face-to-face meeting with
astronaut Andy Thomas, who has been aboard the orbiting Russian
facility since late January.

Discovery is scheduled to dock with the Mir at 11:58 a.m.. central
time tomorrow, marking the ninth meeting between the Shuttle and Mir,
and the first by Discovery. The first seven docking missions were
conducted by Atlantis between June 1995 and September 1997 and the
eighth by Endeavour earlier this year.

In preparation for tomorrow's rendezvous and docking, the astronauts
began assembling the checklists, cameras and other tools they will use
throughout the docking and installed the centerline camera in the
Orbiter Docking System. The centerline camera will provide views of
docking targets and the docking module during the final phase of the
rendezvous activities.

Shortly before 8:35 a.m. Thursday, from a position about eight miles
behind Mir, Commander Charlie Precourt and Pilot Dom Gorie will fire
Discovery's engines in a terminal initiation burn to put Discovery in
position to intercept the orbiting station. The current schedule
shows Discovery arriving 600 feet below the MirSpace Station just
after 10 a.m. central time. Over the course of the next two hours,
Precourt and Gorie will slowly maneuver Discovery into position to
dock with Mir just before noon central time with hatch opening between
the two spacecraft taking place at 1:41 p.m.

Late this afternoon, the crew was given permission to perform an
in-flight maintenance procedure designed to resolve at least part of
the Ku-band communication problem that is preventing video and high
data rate downlink capability. The crew set up a bypass system which
allowed science data from the Alpha Magnetic Spectrometer (AMS) to be
downlinked via S-Band/FM communications when the Shuttle is within
range of a ground station. Confirmation that the IFM procedure was
successful came shortly before 5:30 p.m. when high rate science data
was received at a ground station test facility located near the
Johnson Space Center.

Flight controllers are continuing to evaluate data and consider
options for other work the crew may be asked to perform to try to
regain use of the Ku-Band/Comm mode operation. Mission managers plan
to hold off giving approval for any additional Ku-Band troubleshooting
until after Discovery docks with the Mir station.

Discovery's crew will begin an eight-hour sleep period at 8:06
p.m. this evening and receive a wake-up call from Mission Control at
4:06 a.m. central time tomorrow to begin in earnest their rendezvous
activities.

Discovery is currently in a 203 by 183 nm orbit, circling the Earth
once every 91 minutes.